Add dynamic pagetree / child pages / children to a page

One thing that I miss is the possibility to add a pagetree to the content of a page.
What I expect is to display a list of children of 1) the current page (as default) and optionally 2) the children of an other page that can be specified. In the first place this could be a simple list of the first descendants, optionally displaying more descendant levels. This is basically the same as "Documents" at the bottom of a page or the sidebar navigation.

Once we have tags ( #765 +1 ) it would be also nice to list all pages with a certain tag in the same way in the content.